Excitatory synaptic currents at many (probably most) sites in telencephalon (cortex, limbic system, striatum; about 90% of human brain) and cerebellum occur when the transmitter glutamate is released by input axons onto what are usually referred to as the .alpha.-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid (AMPA), or AMPA/quisqualate, receptors. Drugs that enhance these receptor currents will facilitate communication in brain networks responsible for perceptual-motor integration and higher order behaviors. It is also known from the literature see Arai and Lynch in Brain Research, in press! that such drugs will promote the formation of long-term potentiation, a physiological effect widely held to encode memory.
For example, Ito et al., J. Physiol. Vol. 424:533-543 (1990), discovered that aniracetam, N-anisoyl-2-pyrrolidinone, enhances AMPA receptor mediated currents without affecting currents generated by other classes of receptors. Unfortunately, however, the drug is effective only at high concentrations (.about.1.0 mM) applied directly to the brain. The low potency, limited solubility, and peripheral metabolism of aniracetam limit its utility as an experimental tool and its potential value as a therapeutic. There is a need, therefore, for the design and synthesis of new drugs that are more potent, more soluble and less readily metabolized than aniracetam. Such compounds would provide new tools for manipulating the properties of the AMPA receptor and would be a major step towards a drug that could enhance AMPA receptor function in the brain after peripheral administration.